Electric fuse.



C. W. DAVIS; ELECTRIC FUSE.

APPLICATION FILED MAY 3,1913.

1,1 30,485, Patented Mar. 2, 1915.

WITN ESSESI INVENTOR 'UNITED STATES PATENT OFFICE.

CHARLES W. DAVIS, F EDGEWORTH, PENNSYLVANIA, ASSIGNOR T0 STANDARDUNDERGROUND CABLE COMPANY, OF FITTSBURGH, PENNSYLVANIA, A CORPO- RATIONOF PENNSYLVANIA.

ELECTRIC FUSE.

To all whom it may concern:

- Be it known that 1, CHARLES W. DAVIS, residing at Edgeworth, in thecounty of Allegheny and State of lennsylvania, a citizen of the UnitedStates, have invented or discovered a certain new and useful Improvementin Electric Fuses, of which improvemen-t the following is aspecification.

My invention relates to electric fuses or cut-outs adapted to interruptan electric circuit upon the passage therethrough of abnormal anddangerous currents, and has particularly to do with fuses for hightension currents.

It" is well understood that electric fuses are designed or rated so asto break the cir- I cuit, in which they are placed, when the cur rentcarried thereby reaches or exceeds a predetermined strength] Theconditions,.

under which such fuses become effective, vary' throughout a wide range.First, the

current carried by the circuit may gradually rise until thepredeterminedfusion point of the fuse is reached, the blowing.

thereof under such conditionbeing usuallyattended by a relatively smallexplosion and a correspondingly decreased liabilityof an are beingestablished. Also, when the rise in the current is gradual, the. fusibleelement heats up slowly, and during such heating period the circuit willremain closed and.

will be subjected to a current of greater strength than it is intendedto carry. In

the second'place, a short circuit of substantially any strength inexcess of the-fuse rating may almost instantaneously traverse thecircuit, causing the fuse to blow with a violent explosion, and verymaterially increasing the liability of a continued arc, beingestablished.

It is the object of my present invention to provide a fuse or cut-out,whereby the rapidity and extent or intensity of the circuitsinterruption will vary according to the character of the currenttraversing the circuit and causing such interruption.

In the accompanying drawing I have illustrated in vertical section asingle embodiment of my invention. s

Having reference first to the constructio of the fuse illustratedherein, and subsequently to its operation under the varying conditionsof service, the complete structure is placed in a fuse box 1, throughthe Specification of LettersPat-ent.

Patented Mar. 2, 1915;

\ a iieationfiieana s, 191a Seria1No.765,184.

contactor consisting preferably of a tube 7- having a plurality ofspring arms at its lower end, adapted to electrically engage or contactwith the inner surface of said sleeve 4. The upper end of the fusecasing is closed by meansof a suitable plug 8, provided with a bindingpost 9; and a fuse strip, comprising a low fusion portion 10 andadjoining higher fusion portions 11 and 12,'is placed in the upperportion of the casing, the portion 11 being electrically connected tothe binding post 9, and the portion 12 to the contactor 7 by means of asuitable flexible conductor 13,, which preferably eX- te'nds' throughand is secured to a suitable pressure-resisting movable abutment 20. Thecasing 5 is loosely mounted for vertical movement in a tube 14, which issecured to a transversely extending support 21 of insulating material,which in turn is supported. by rods 22. The arrangement is such thatgases, generated upon the blowing of the fusible element 10,-will exerttheir expansive forces longitudinally of the casing 5 and cause it. tomove vertically, carrying with it the contactor 7 thereby disengaging itfrom the contactor a. A second means is also provided for moving thefuse. casing to effect a disengagement of the contactors l and 7, suchmeans being effective upon the flowing of an abnormal current throughthe circuit, but independent of the explosive action of the fuse strip.As illustrated herein,"surh means consists of an electromagnetic coiland a core or plunger adapted to engage the fuse casing 5, preferablystriking it a hammer blow as it is drawn into the magnetic field of thecoil, the arrangement being such that the plunger will not be caused tomove until the current flowing through the fuse has exceeded the fuserating.

Referring again to the drawing, the plunger is, in this embodiment of myinvention, a tube 15 loosely surrounding the fuse casing 5 andvertically movable with relation thereto, the lower end of the tuberesting upon the support-21. A plunger-engaging abutment 16 projectsfrom the side of the casing 5 in the path of movement of the plunger andabove the upper end thereof, the arrangement being such that themovement of .merged in a body of arc-dampening liquid,

such as oil or carbon tetra-chlorid. When the fuse box L is filled \withsuch a liquid to a point above the level of the top of the casing 5,suitable holes 18 and 19 may be placed in the lower and upper ends,respectively, of such casing so. that the find may circulatetherethrough and thus cool the fusible element .10. If, however, it isdesirable to have the fusible element 10 unsurrounded by such liquid theupper casing holesmay be placed below the fusible element 10 asindicated at 19 in which event a fuse-containing pocket will be formed1n the upper portion of the casing 5. Such pocket may be filled with aninert granular material, such as slaked lime or magnesia, or the pocketmay be simply an air-pocket, the air pressure varying according to thelevel of the liquid within the fuse box.

When, inthe operation of the fuse, the current carried by the circuitgradually rises to and above the rated capacity of the fusible element10, the plunger 15, being.

drawn within the coil 17, strikes the casing abutment 16 and lifts thecasing 5, thus disengaging the contactors 4 and 7. As will be readilyseen, theadvantageof such an arrangement is that the circuit will beeffectually opened even though the are formed by the blowing of. thefuse should hold on, in which event theexpansion of the gases will expelthe relatively cool liquid from the lower end -of the. casing 5 andbetween the two contactors 4 and 7,

v thus more effectually quenching the are at this point Also, thegapbetween the free ends of the high fusion portions 11 and 12 will bewidened. k Incase the circuit is short-circuited bya current ofmaterially greater strength than the rated capacity of the fusibleelement 10, such element will be fused almost instantaneously. Theplunger will, in this event, impart a hammer blow to the casing 5, thusovercoming the initial frictional resistance "betweenthe contactors 4and 7, which contactors will be separated both by the action of theelectro-magnet and by the explosive forces of the fuse.

within said casing,

I claim as my invention: 1. In an electric fuse, the combination of afuse box containing a bodyof arc-dampening liquid, a. pairof contactorssubmerged in said liquid and movable to and from engagement with eachother, a casing secured to one of said contactors, afuse strip withinthe casing, and means for ap-.

plying the explosive force of said fuse when blown to separate saidcontactors and to force a stream of arc-dampening liquid between themwhen separated.

2. In an electric fuse, the combination of a fuse box containing a bodyof arcdampenlng liquid, a fixed contactor submerged in the liquid, afuse casing provided with a contactor movable to andfrom engagement withthe first named contactor and adapted to contain a portion of the liquidwithin the fuse box, an expulsion opening in said casing adjacent tothepoint of engagement of said'contactors, a fuse strip within saidcasing, and means for applying the explosive force of said fuse stripwhen blown to move the contactor borne by the casing from its engagementwith said fixed contactor and to expel the liquid from the fuse casingthrough said opening and between the separated contactors.

3. In an electric fuse, the combination of a contactor, a movable fusecasing provided with a contactor adapted to electrically engage saidfirst-named contactor, a fuse strip and means efiective upon the passageof an abnormal current through said fuse strip to engage and move saidcasing, therebydisengaging said contactors.

4. In an electric fuse, the combination of a contactor, a movablefusecasing provided with a contactor adapted to electrically engage saidfirst-named contactor, a fuse strip within said casing, anelectro-magnet havmg its coil in circuit with said fuse and a movableplunger in the magnetic field of said coil and means for applying themovmg force of said plunger to said casing upon the passage of anabnormal current through said fuse.

5. In an electric fuse, the combination of .a fuse-box containing a bodyof arc-dampening liquid, a contactor submerged in said llquld, a movablefuse casing provided with anexpulsion opening beneath the surface ofsaid liquid, a contactor secured to and a fuse strip within said casing,and means effective upon the passage of an abnormal current through saidfuse strip to move said casing for disengaging said contactors, andmeans for applying the expansive forces of the gases of fusion generatedby the blowing of said fuse strip to expel the liq'uidfrom said casingand between said disengaged contactors.

6. In an electric fuse, the combination of a fuse box containing a bodyof arc-dam-- a fuse casing provided with an expulsion pening liquid, apair of engaging but separable oontactors submerged in said liquid,

opening adjacent to said contactors and below the level of the liquidWithin said box, a fuse strip Within said casing, means effective uponthe passage of an abnormal current through said fuse to disengage saidcontactors, and means for applying the ex-.

pensive forces of the gases of fusion generated by the blowing of saidfuse strip to expel the liquid from said casing and be: tween saiddisengaged contactors.

7. in an electric fuse, the combination of a fuse box containing a bodyof arc-dampening liquid, a fixed contactor in said box, avertically-disposed and vertically-movable fuse casing closed at itsupper end and open casing adjacent to its open lower end and adapted toelectrically engage said firstnamed contactor, a fuse strip within theupper portion of said casing, an electromagnet haying itscoil in circuitwith said strip, a movable plunger in the magnetic field of said coil,and means for applying the moving force of said plunger to dislodge saidcasing upon the passage of an abnormal current through said fuse strip.

In testimony whereof I have hereunto set my hand. CHARLES W. DAVIS.

Witnesses:

R. W, WHITE, FRANGIS J. TomAssoN.

at its lower end, a contactor secured to said

